Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek
[7] oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "severalPerWeek" "none" "oncePerWeek"
sample( lvs, 3 )
[1] "daily" "severalPerWeek" "oncePerWeek"
sample( lvs, 3 )
[1] "severalPerWeek" "daily" "none"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] severalPerWeek oncePerWeek oncePerWeek severalPerWeek oncePerWeek daily
[7] severalPerWeek none daily none severalPerWeek severalPerWeek
[13] none severalPerWeek none oncePerWeek daily none
[19] daily none none none oncePerWeek daily
[25] oncePerWeek none oncePerWeek none oncePerWeek oncePerWeek
[31] severalPerWeek oncePerWeek daily oncePerWeek daily oncePerWeek
[37] none daily oncePerWeek oncePerWeek severalPerWeek oncePerWeek
[43] daily daily none severalPerWeek daily none
[49] daily none severalPerWeek oncePerWeek none none
[55] daily severalPerWeek oncePerWeek severalPerWeek oncePerWeek none
[61] daily none oncePerWeek severalPerWeek daily severalPerWeek
[67] severalPerWeek none daily daily daily daily
[73] oncePerWeek daily oncePerWeek none daily daily
[79] oncePerWeek severalPerWeek oncePerWeek severalPerWeek severalPerWeek daily
[85] oncePerWeek oncePerWeek daily oncePerWeek oncePerWeek oncePerWeek
[91] none oncePerWeek oncePerWeek daily oncePerWeek severalPerWeek
[97] none oncePerWeek none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 24
2 oncePerWeek 32
3 severalPerWeek 19
4 daily 25
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 25
2 severalPerWeek 19
3 oncePerWeek 32
4 none 24